Immunity induction agent

ABSTRACT

Provided is a novel immunity-inducing agent useful as a therapeutic and/or prophylactic agent for cancer. The immunity-inducing agent comprises as an effective ingredient(s) at least one polypeptide having immunity-inducing activity selected from the polypeptides (a), (b) and (c) below, and/or a recombinant vector(s) that comprise(s) a polynucleotide(s) encoding the at least one polypeptide, which recombinant vector(s) is/are capable of expressing the polypeptide(s) in vivo: (a) a polypeptide composed of not less than 7 consecutive amino acids in any one of the amino acid sequences of SEQ ID NOs:4, 2, 22 and 24 in SEQUENCE LISTING; (b) a polypeptide having a sequence identity of not less than 90% to the polypeptide (a) and composed of not less than 7 amino acids; and (c) a polypeptide comprising the polypeptide (a) or (b) as a partial sequence thereof.

TECHNICAL FIELD

The present invention relates to a novel immunity-inducing agent useful as a therapeutic and/or prophylactic agent for cancer.

BACKGROUND ART

Cancer is the commonest cause for death among all of the causes for death, and therapies carried out therefor at present are mainly surgical treatment, which may be carried out in combination with radiotherapy and/or chemotherapy. In spite of the developments of new surgical methods and discovery of new anti-cancer agents in recent years, treatment results of cancers have not been improved very much so far except for some cancers. In recent years, by virtue of the development in molecular biology and cancer immunology, cancer antigens recognized by cytotoxic T cells reactive with cancers, as well as the genes encoding cancer antigens, were identified, and expectations for antigen-specific immunotherapies have been raised.

In immunotherapy, in order to reduce side effects, the peptide or protein to be recognized as the antigen needs to be hardly present in normal cells, and to be specifically present in cancer cells. In 1991, Boon et al. of Ludwig Institute in Belgium isolated a human melanoma antigen MAGE 1, which is recognized by CD8-positive T cells, by a cDNA-expression cloning method using an autologous cancer cell line and cancer-reactive T cells (Non-patent Document 1). Thereafter, the SEREX (serological identifications of antigens by recombinant expression cloning) method, wherein tumor antigens recognized by antibodies produced in the living body of a cancer patient in response to the patient's own cancer are identified by application of a gene expression cloning method, was reported (Patent Document 1, Non-patent Document 2), and several cancer antigens have been isolated by this method. Using a part of the cancer antigens as targets, clinical tests for cancer immunotherapy have started.

On the other hand, as in human, a number of tumors such as mammary gland tumor and squamous cell carcinoma are known in dogs and cats, and they rank high also in the statistics of diseases in dogs and cats. However, no therapeutic agent, prophylactic agent or diagnostic agent effective for cancers in dogs or cats exists at present. Since most tumors in dogs and cats are realized by their owners only after the tumors grew larger due to the progression, their visit to the hospital is already too late, and even if they receive surgical excision or administration of a human drug (an anticancer drug or the like), they often die shortly after the treatment. Under such circumstances, if therapeutic agents and prophylactic agents for cancer effective for dogs and cats become available, their uses for dog cancers are expected to be developed.

Stearoyl-CoA desaturase 1 (SCD1) introduces a double bond to the C9-C10 position of a saturated fatty acid. Preferred substrates for the enzyme are palmitoyl-CoA (16:0) and stearoyl-CoA (18:0), and these are converted to palmitoleoyl-CoA (16:1) and oleoyl-CoA (18:1), respectively. The obtained monounsaturated fatty acid can then be used in vivo for preparation of phospholipids, triglycerides and cholesteryl esters. Further, various cancers such as liver cancer, esophagus cancer and colon cancer show increased expression of SCD1, and it has been reported that inhibition of the function of SCD1 with siRNA or a low-molecular-weight compound causes suppression of the cell growth or induction of apoptosis (Non-patent Documents 3, 4 and 5). However, there is no report suggesting that SCD1 protein has immunity-inducing activity against cancer cells and hence that the protein is useful for treatment or prophylaxis of cancer.

PRIOR ART DOCUMENTS Patent Document

-   [Patent Document 1] U.S. Pat. No. 5,698,396 B

Non-patent Documents

-   [Non-patent Document 1] Bruggen P. et al., Science, 254:1643-1647     (1991) -   [Non-patent Document 2] Proc. Natl. Acad. Sci. USA, 92: 11810-11813     (1995) -   [Non-patent Document 3] Scaglia N. et al., PLoS One 4: e6812 (2009) -   [Non-patent Document 4] Morgan-Lappe S E. et al., Cancer Res 67:     4390-4398 (2007) -   [Non-patent Document 5] Scaglia N. et al., Biochim Biophys Acta     1687: 141-151 (2005) -   [Non-patent Document 6] Ariyama H. et al., J Biol Chem (2010)

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The present invention aims to discover a novel polypeptide useful for a therapeutic and/or prophylactic agent for cancer, and to provide the polypeptide for use in an immunity-inducing agent.

Means for Solving the Problems

By the SEREX method using a dog testis-derived cDNA library and serum obtained from a tumor-bearing dog, the present inventors intensively studied to obtain a cDNA encoding a protein which binds to antibodies present in serum derived from a tumor-bearing living body, and, based on the cDNA, a polypeptide of dog stearoyl-CoA desaturase 1 (hereinafter referred to as SCD1) having the amino acid sequence of SEQ ID NO:2 was prepared. Further, based on human and mouse homologous genes of the obtained gene, human and mouse SCD1s having the amino acid sequences of SEQ ID NOs:4 and 6 were prepared. Further, the present inventors discovered that these SCD1 polypeptides are specifically expressed in tissues or cells of breast cancer, brain tumor, colon cancer, perianal adenocarcinoma, mastocytoma, neuroblastoma, renal cancer, liver cancer, lung cancer, prostate cancer and leukemia. The present inventors further discovered that administration of the SCD1 to a living body enables induction of immunocytes against SCD1 in the living body and regression of a tumor expressing SCD1 in the living body. Further, the present inventors discovered that a recombinant vector which can express a polynucleotide encoding the SCD1 polypeptide or a fragment thereof induces an antitumor effect against cancer expressing SCD1 in a living body.

Further, the present inventors discovered that an SCD1 polypeptide has a capacity to be presented by antigen-presenting cells to cause activation and the growth of cytotoxic T cells specific to the peptide (immunity-inducing activity), and therefore that the polypeptide is useful for therapy and/or prophylaxis of cancer. Further, the present inventors discovered that antigen-presenting cells which have contacted with the polypeptide, and T cells which have contacted with the antigen-presenting cells, are useful for therapy and/or prophylaxis of cancer, thereby completing the present invention.

Thus, the present invention has the following characteristics.

(1) An immunity-inducing agent comprising as an effective ingredient(s) at least one polypeptide having immunity-inducing activity selected from the polypeptides (a) to (c) below, and/or a recombinant vector(s) that comprise(s) a polynucleotide(s) encoding the at least one polypeptide, the recombinant vector(s) being capable of expressing the polypeptide(s) in vivo:

(a) a polypeptide composed of not less than 7 consecutive amino acids in any one of the amino acid sequences of SEQ ID NOs:4, 2, 22 and 24 in SEQUENCE LISTING;

(b) a polypeptide having a sequence identity of not less than 85% to the polypeptide (a) and composed of not less than 7 amino acids; and

(c) a polypeptide comprising the polypeptide (a) or (b) as a partial sequence thereof.

(2) The immunity-inducing agent according to (1), wherein the polypeptide having immunity-inducing activity is a polypeptide having the amino acid sequence of SEQ ID NO:4, 2, 22 or 24 in SEQUENCE LISTING. (3) The immunity-inducing agent according to (1) or (2), which is an agent for treating antigen-presenting cells. (4) The immunity-inducing agent according to (1) or (2), which is a therapeutic and/or prophylactic agent for a cancer(s). (5) The immunity-inducing agent according to (4), wherein the cancer(s) is/are a cancer(s) expressing SCD1. (6) The immunity-inducing agent according to (4) or (5), wherein the cancer(s) is/are breast cancer, brain tumor, colon cancer, perianal adenocarcinoma, mastocytoma, neuroblastoma, renal cancer, liver cancer, lung cancer, prostate cancer and/or leukemia. (7) The immunity-inducing agent according to any one of (1) to (6), further comprising an immunoenhancer. (8) The immunity-inducing agent according to (7), wherein the immunoenhancer is at least one selected from the group consisting of Freund's incomplete adjuvant; Montanide; poly-LC and derivatives thereof; CpG oligonucleotides; interleukin-12; interleukin-18; interferon-α; interferon-β; interferon-ω; interferon-γ; and Flt3 ligand.

Effect of the Invention

By the present invention, a novel immunity-inducing agent useful for therapy, prophylaxis and/or the like of cancer is provided. As concretely described in the later-mentioned Examples, administration of the polypeptide used in the present invention to a living body enables induction of immunocytes in the living body, and a cancer which has already occurred can be reduced or regressed. Therefore, the polypeptide is useful for therapy and/or prophylaxis of cancer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the expression patterns of the identified SCD1 gene in dog normal tissues, tumor tissues and cancer cell lines. Reference numeral 1, the expression patterns of the dog SCD1 gene in various dog tissues and cell lines; reference numeral 2, the expression patterns of the dog GAPDH gene in various dog tissues and cell lines.

FIG. 2 shows the expression patterns of the identified SCD1 gene in human normal tissues, tumor tissues and cancer cell lines. Reference numeral 3, the expression patterns of the human SCD1 gene in various human tissues and cell lines; reference numeral 4, the expression patterns of the human GAPDH gene in various human tissues and cell lines.

FIG. 3 shows the expression patterns of the identified SCD1 gene in mouse normal tissues, tumor tissues and cancer cell lines. Reference numeral 5, the expression patterns of the mouse SCD1 gene in various mouse tissues and cell lines; reference numeral 6, the expression patterns of the mouse GAPDH gene in various mouse tissues and cell lines.

BEST MODE FOR CARRYING OUT THE INVENTION

Examples of the polypeptide contained in the immunity-inducing agent of the present invention as an effective ingredient include the following. In the present invention, the term “polypeptide” means a molecule formed by a plurality of amino acids linked together by peptide bonds, and includes not only polypeptide molecules having large numbers of amino acids constituting them, but also low-molecular-weight molecules having small numbers of amino acids (oligopeptides), and full-length proteins. The present invention also includes the full-length SCD1 proteins having the amino acid sequence of SEQ ID NO:4, 2, 22 or 24.

(a) A polypeptide that is composed of not less than 7 consecutive amino acids in a polypeptide having the amino acid sequence of SEQ ID NO:4, 2, 22 or 24 in SEQUENCE LISTING, and has an immunity-inducing activity.

(b) A polypeptide composed of not less than 7 amino acids, which polypeptide has a sequence identity of not less than 85% to the polypeptide (a) and an immunity-inducing activity.

(c) A polypeptide that comprises the polypeptide (a) or (b) as a partial sequence thereof, and has an immunity-inducing activity.

In the present invention, the term “having an amino acid sequence” means that amino acid residues are arrayed in such an order. Therefore, for example, “polypeptide having the amino acid sequence of SEQ ID NO:2” means the polypeptide having the amino acid sequence of Met Pro Ala His . . . (snip) . . . Tyr Lys Ser Gly shown in SEQ ID NO:2, which polypeptide has a size of 360 amino acid residues. Further, for example, “polypeptide having the amino acid sequence of SEQ ID NO:2” may be referred to as “polypeptide of SEQ ID NO:2” for short. This also applies to the term “having a base sequence”. In this case, the term “having” may be replaced with the expression “composed of”.

As used herein, the term “immunity-inducing activity” means an ability to induce immunocytes that secrete cytokines such as interferon in a living body.

Whether or not the polypeptide has an immunity-inducing activity can be confirmed using, for example, the known ELISPOT assay. More specifically, for example, as described in the Examples below, cells such as peripheral blood mononuclear cells are obtained from a living body subjected to administration of the polypeptide whose immunity-inducing activity is to be evaluated, and the obtained cells are then cocultured with the polypeptide, followed by measuring the amount(s) of a cytokine(s) produced by the cells using a specific antibody/antibodies, thereby enabling measurement of the number of immunocytes among the cells. By this, evaluation of the immunity-inducing activity is possible.

Alternatively, as described in the later-mentioned Examples, administration of the recombinant polypeptide of any of (a) to (c) described above to a tumor-bearing animal allows regression of the tumor by its immunity-inducing activity. Thus, the above immunity-inducing activity can be evaluated also as an ability to suppress the growth of cancer cells or to cause reduction or disappearance of a cancer tissue (tumor) (hereinafter referred to as “antitumor activity”). The antitumor activity of a polypeptide can be confirmed by, for example, as more specifically described in the Examples below, observation of whether or not a tumor is reduced when the polypeptide was actually administered to a tumor-bearing living body.

Alternatively, the antitumor activity of a polypeptide can be evaluated also by observation of whether or not T cells stimulated with the polypeptide (that is, T cells brought into contact with antigen-presenting cells presenting the polypeptide) show a cytotoxic activity against tumor cells in vitro. The contact between the T cells and the antigen-presenting cells can be carried out by their coculture in a liquid medium, as mentioned below. Measurement of the cytotoxic activity can be carried out by, for example, the known method called ⁵¹Cr release assay described in Int. J. Cancer, 58: p 317, 1994. In cases where the polypeptide is to be used for therapy and/or prophylaxis of cancer, the evaluation of the immunity-inducing activity is preferably carried out using the antitumor activity as an index, although the index is not limited thereto.

Each of the amino acid sequences of SEQ ID NOs:2, 4, 22 and 24 in SEQUENCE LISTING disclosed in the present invention is an amino acid sequence of SCD1 that was isolated, by the SEREX method using a dog testis-derived cDNA library and serum of a tumor-bearing dog, as a polypeptide that specifically binds to an antibody existing in the serum of a tumor-bearing dog, or a homologous factor of the polypeptide in human, cow or horse (see Example 1). Human SCD 1, which is the human homologous factor of dog SCD1, has a sequence identity of 89% in terms of the base sequence and 90% in terms of the amino acid sequence; bovine SCD1, which is the bovine homologous factor, has a sequence identity of 88% in terms of the base sequence and 87% in terms of the amino acid sequence; and equine SCD1, which is the equine homologous factor, has a sequence identity of 90% in terms of the base sequence and 87% in terms of the amino acid sequence.

The polypeptide (a) is a polypeptide composed of not less than 7 consecutive, preferably 8, 9 or not less than 10 consecutive, amino acids in the polypeptide having the amino acid sequence of SEQ ID NO:2, 4, 22 or 24, and has an immunity-inducing activity. The polypeptide is more preferably a polypeptide composed of an amino acid sequence having a sequence identity of not less than 85% to the amino acid sequence of SEQ ID NO:4, and the polypeptide especially preferably has the amino acid sequence of SEQ ID NO:2, 4, 22 or 24. As is known in the art, a polypeptide having not less than about 7 amino acid residues can exert its antigenicity and immunogenicity. Thus, a polypeptide having not less than 7 consecutive amino acid residues in the amino acid sequence of SEQ ID NO:2, 4, 22 or 24 can have an immunity-inducing activity, so that the polypeptide can be used for preparation of the immunity-inducing agent of the present invention.

As a principle of immune induction by administration of a cancer antigenic polypeptide, the following process is known: a polypeptide is incorporated into an antigen-presenting cell and then degraded into smaller fragments by peptidases in the cell, followed by being presented on the surface of the cell. The fragments are then recognized by a cytotoxic T cell or the like that selectively kills cells presenting the antigen. The size of the polypeptide presented on the surface of the antigen-presenting cell is relatively small and about 7 to 30 amino acids. Therefore, from the viewpoint of presenting the polypeptide on the surface of the antigen-presenting cell, one preferred mode of the above-described polypeptide (a) is a polypeptide composed of about 7 to 30 consecutive amino acids in the amino acid sequence of SEQ ID NO:2, 4, 22 or 24, and more preferably, a polypeptide composed of about 8 to 30 or about 9 to 30 amino acids is sufficient as the polypeptide (a). In some cases, these relatively small polypeptides are presented directly on the surface of antigen-presenting cells without being incorporated into the antigen-presenting cells.

Further, a polypeptide incorporated into an antigen-presenting cell is cleaved at random sites by peptidases in the cell to yield various polypeptide fragments, which are then presented on the surface of the antigen-presenting cell. Therefore, administration of a large polypeptide such as the full-length region of SEQ ID NO:2, 4, 22 or 24 inevitably causes production of polypeptide fragments by degradation in the antigen-presenting cell, which fragments are effective for immune induction via the antigen-presenting cell. Therefore, also for immune induction via antigen-presenting cells, a large polypeptide can be preferably used, and the polypeptide may be composed of not less than 30, preferably not less than 100, more preferably not less than 200, still more preferably not less than 250 amino acids. The polypeptide may be still more preferably composed of the full-length region of SEQ ID NO:2, 4, 22 or 24.

The polypeptide (b) is the same polypeptide as the polypeptide (a) except that a small number of (preferably, one or several) amino acid residues are substituted, deleted and/or inserted, which has a sequence identity of not less than 90%, preferably not less than 95%, more preferably not less than 98%, still more preferably not less than 99% or not less than 99.5% to the original sequence and has an immunity-inducing activity. It is well known in the art that, in general, there are cases where a protein antigen retains almost the same antigenicity as the original protein even if the amino acid sequence of the protein is modified such that a small number of amino acid residues are substituted, deleted and/or inserted. Therefore, since the polypeptide (b) may also exert an immunity-inducing activity, it can be used for preparation of the immunity-inducing agent of the present invention. Further, the polypeptide (b) is also preferably a polypeptide having the same amino acid sequence as the amino acid sequence of SEQ ID NO:2, 4, 22 or 24 except that one or several amino acid residues are substituted, deleted and/or inserted. As used herein, the term “several” means an integer of 2 to 10, preferably an integer of 2 to 6, more preferably an integer of 2 to 4.

As used herein, the term “sequence identity” of amino acid sequences or base sequences means the value calculated by aligning two amino acid sequences (or base sequences) to be compared such that the number of matched amino acid residues (or bases) is maximum between the amino acid sequences (or base sequences), and dividing the number of matched amino acid residues (or the number of matched bases) by the total number of amino acid residues (or the total number of bases), which value is represented as a percentage. When the alignment is carried out, one or more gaps are inserted into one or both of the two sequences to be compared as required. Such alignment of sequences can be carried out using a well-known program such as BLAST, PASTA or CLUSTAL W. When one or more gaps are inserted, the above-described total number of amino acid residues is the number of residues calculated by counting one gap as one amino acid residue. When the thus counted total number of amino acid residues is different between the two sequences to be compared, the sequence identity (%) is calculated by dividing the number of matched amino acid residues by the total number of amino acid residues in the longer sequence.

The 20 types of amino acids constituting naturally occurring proteins may be classified into groups in each of which similar properties are shared, for example, into neutral amino acids with side chains having low polarity (Gly, Ile, Val, Leu, Ala, Met, Pro), neutral amino acids having hydrophilic side chains (Asn, Gln, Thr, Ser, Tyr, Cys), acidic amino acids (Asp, Glu), basic amino acids (Arg, Lys, His) and aromatic amino acids (Phe, Tyr, Trp). It is known that, in many cases, substitution of an amino acid within the same group does not change the properties of the polypeptide. Therefore, in cases where an amino acid residue in the polypeptide (a) of the present invention is substituted, the probability that the immunity-inducing activity can be maintained may be increased by carrying out the substitution within the same group, which is preferred.

The polypeptide (c) is a polypeptide that comprises the polypeptide (a) or (b) as a partial sequence and has an immunity-inducing activity. That is, the polypeptide (c) is a polypeptide in which one or more amino acids and/or one or more polypeptides is added at one or both ends of the polypeptide (a) or (b), and has an immunity-inducing activity. Such a polypeptide can also be used for preparation of the immunity-inducing agent of the present invention.

The above-described polypeptides can be synthesized by, for example, a chemical synthesis method such as the Fmoc method (fluorenylmethyloxycarbonyl method) or the tBoc method (t-butyloxycarbonyl method). Further, they can be synthesized by conventional methods using various types of commercially available peptide synthesizers. Further, the polypeptide of interest can be obtained using known genetic engineering techniques by preparing a polynucleotide encoding the polypeptide and incorporating the polynucleotide into an expression vector, followed by introducing the resulting vector into a host cell and allowing the host cell to produce the polypeptide therein.

The polynucleotide encoding the above polypeptide can be easily prepared by a known genetic engineering technique or a conventional method using a commercially available nucleic acid synthesizer. For example, DNA having the base sequence of SEQ ID NO:1 can be prepared by carrying out PCR using a dog chromosomal DNA or cDNA library as a template, and a pair of primers designed such that the base sequence of SEQ ID NO:1 can be amplified therewith. DNA having the base sequence of SEQ ID NO:3 can be similarly prepared by using a human chromosomal DNA or cDNA library as the template. The reaction conditions for the PCR can be set appropriately, and examples of the reaction conditions include, but are not limited to, repeating the reaction process of 94° C. for 30 seconds (denaturation), 55° C. for 30 seconds to 1 minute (annealing) and 72° C. for 2 minutes (extension) for, for example, 30 cycles, followed by the reaction at 72° C. for 7 minutes. Further, the desired DNA can be isolated by preparing an appropriate probe or primer based on the information of the base sequence or the amino acid sequence of SEQ ID NO:1 or 3 in SEQUENCE LISTING in the present description, and screening a cDNA library of dog, human or the like using the probe or primer. The cDNA library is preferably prepared from cells, an organ or a tissue expressing the protein of SEQ ID NO:2 or 4. The above-described operations such as preparation of the probe or primer, construction of the cDNA library, screening of the cDNA library and cloning of the gene of interest are known to those skilled in the art, and can be carried out according to the methods described in Molecular Cloning, Second Edition; Current Protocols in Molecular Biology; and/or the like. From the thus obtained DNA, DNA encoding the polypeptide (a) can be obtained. Further, since the codons encoding each amino acid are known, the base sequence of a polynucleotide encoding a specific amino acid sequence can be easily specified. Therefore, since the base sequence of a polynucleotide encoding the polypeptide (b) or polypeptide (c) can also be easily specified, such a polynucleotide can also be easily synthesized using a commercially available nucleic acid synthesizer according to a conventional method.

The host cells are not restricted as long as the cells can express the above-described polypeptide, and examples of the cells include, but are not limited to, prokaryotic cells such as E. coli; and eukaryotic cells such as mammalian cultured cells including monkey kidney cells COS1 and Chinese hamster ovary cells CHO; budding yeast; fission yeast; silkworm cells; and Xenopus laevis egg cells.

In cases where prokaryotic cells are used as the host cells, an expression vector containing an origin that enables replication of the vector in a prokaryotic cell, promoter, ribosome binding site, DNA cloning site, terminator and/or the like is used. Examples of the expression vector for E. coli include the pUC system, pBluescriptII, pET expression system and pGEX expression system. By incorporating a DNA encoding the above polypeptide into such an expression vector and transforming prokaryotic host cells with the vector, followed by culturing the resulting transformants, the polypeptide encoded by the DNA can be expressed in the prokaryotic host cells. In such a case, the polypeptide can also be expressed as a fusion protein with another protein.

In cases where, eukaryotic cells are used as the host cells, an expression vector for eukaryotic cells, comprising a promoter, splicing site, poly(A) addition site and/or the like is used as the expression vector. Examples of such an expression vector include pKA1, pCDM8, pSVK3, pMSG, pSVL, pBK-CMV, pBK-RSV, EBV vector, pRS, pcDNA3, pMSG and pYES2. Similarly to the above case, by incorporating a DNA encoding the above polypeptide into such an expression vector and transforming eukaryotic host cells with the vector, followed by culturing the resulting transformants, the polypeptide encoded by the DNA can be expressed in the eukaryotic host cells. In cases where pIND/V5-His, pFLAG-CMV-2, pEGFP-N1, pEGFP-C1 or the like is used as the expression vector, the above polypeptide can be expressed as a fusion protein comprising a tag such as a His tag, FLAG tag, myc tag, HA tag or GFP.

For the introduction of the expression vector into host cells, a well-known method such as electroporation, the calcium phosphate method, the liposome method or the DEAE dextran method may be used.

Isolation and purification of the polypeptide of interest from the host cells can be carried out by a combination of known separation operations. Examples of the known separation operations include, but are not limited to, treatment with a denaturant such as urea or with a surfactant; ultrasonication treatment; enzyme digestion; salting-out or solvent fractional precipitation; dialysis; centrifugation; ultrafiltration; gel filtration; SDS-PAGE; isoelectric focusing; ion-exchange chromatography; hydrophobic chromatography; affinity chromatography; and reversed-phase chromatography.

The polypeptides obtained by the above methods also include, as mentioned above, those in the form of a fusion protein with another arbitrary protein. Examples of such polypeptides include fusion proteins with glutathion S-transferase (GST) and fusion proteins with a His tag. Such a polypeptide in the form of a fusion protein is also included within the scope of the present invention as the above-described polypeptide (c). Further, in some cases, the polypeptide expressed in a transformed cell is modified in various ways in the cell after translation. Such a post-translationally modified polypeptide is also included within the scope of the present invention as long as it has an immunity-inducing activity. Examples of such a post-translational modification include: elimination of N-terminal methionine; N-terminal acetylation; glycosylation; limited degradation by an intracellular protease; myristoylation; isoprenylation; and phosphorylation.

As described more concretely in the later-mentioned Examples, administration of the polypeptide having an immunity-inducing activity to a tumor-bearing living body enables regression of an already existing tumor. Therefore, the immunity-inducing agent of the present invention can be used as a therapeutic and/or prophylactic agent for cancer. Further, the polypeptide having an immunity-inducing activity can be used for a method of therapy and/or prophylaxis of cancer by immune induction.

As used herein, the terms “tumor” and “cancer” mean a malignant neoplasm, and are used interchangeably

In this case, the cancer to be treated is not restricted as long as SCD1 is expressed in the cancer, and the cancer is preferably breast cancer, brain tumor, colon cancer, perianal adenocarcinoma, mastocytoma, neuroblastoma, renal cancer, liver cancer, lung cancer, prostate cancer or leukemia.

The subject animal is preferably a mammal, more preferably a mammal such as a primate, pet animal, domestic animal or sport animal, especially preferably human, dog or cat.

The administration route of the immunity-inducing agent of the present invention to a living body may be either oral administration or parenteral administration, and is preferably parenteral administration such as intramuscular administration, subcutaneous administration, intravenous administration or intraarterial administration. In cases where the immunity-inducing agent is used for therapy of cancer, it may be administered to a regional lymph node in the vicinity of the tumor to be treated, as described in the Examples below, in order to enhance its anticancer activity. The dose may be any dose as long as the dose is effective for immune induction, and, for example, in cases where the agent is used for therapy and/or prophylaxis of cancer, the dose may be one effective for therapy and/or prophylaxis of the cancer. The dose effective for therapy and/or prophylaxis of cancer is appropriately selected depending on the size, symptoms and the like of the tumor, and the effective dose is usually 0.0001 μg to 1000 μg, preferably 0.001 μg to 1000 μg per subject animal per day. The agent may be administered once, or dividedly in several times. The agent is preferably administered dividedly in several times, every several days to several months. As concretely shown in the Examples below, the immunity-inducing agent of the present invention can cause regression of an already occurred tumor. Therefore, since the agent can exert its anticancer activity also against a small number of cancer cells at an early stage, development or recurrence of cancer can be prevented by using the agent before development of the cancer or after therapy for the cancer. That is, the immunity-inducing agent of the present invention is effective for both therapy and prophylaxis of cancer.

The immunity-inducing agent of the present invention may contain only a polypeptide or may be formulated by being mixed as appropriate with an additive such as a pharmaceutically acceptable carrier, diluent or vehicle suitable for each administration mode. Formulation methods and additives which may be used are well-known in the field of formulation of pharmaceuticals, and any of the methods and additives may be used. Specific examples of the additives include, but are not limited to, diluents such as physiological buffer solutions; vehicles such as sugar, lactose, corn starch, calcium phosphate, sorbitol and glycine; binders such as syrup, gelatin, gum arabic, sorbitol, polyvinyl chloride and tragacanth; and lubricants such as magnesium stearate, polyethylene glycol, talc and silica. Examples of the formulation include oral preparations such as tablets, capsules, granules, powders and syrups; and parenteral preparations such as inhalants, injection solutions, suppositories and solutions. These formulations may be prepared by commonly known production methods.

The immunity-inducing agent of the present invention may be used in combination with an immunoenhancer capable of enhancing the immune response in a living body. The immunoenhancer may be contained in the immunity-inducing agent of the present invention or administered as a separate composition to a patient in combination with the immunity-inducing agent of the present invention.

Examples of the immunoenhancer include adjuvants. Adjuvants can enhance the immune response by providing a reservoir of antigen (extracellularly or inside macrophages), activating macrophages and stimulating specific sets of lymphocytes, thereby enhancing the immune response and hence the anticancer action. Therefore, especially in cases where the immunity-inducing agent of the present invention is used for therapy and/or prophylaxis of cancer, the immunity-inducing agent preferably comprises an adjuvant, in addition to the above-described polypeptide as an effective ingredient. Many types of adjuvants are well known in the art, and any of these adjuvants may be used. Specific examples of the adjuvants include MPL (SmithKline Beecham), homologues of Salmonella minnesota Re 595 lipopolysaccharide obtained after purification and acid hydrolysis of the lipopolysaccharide; QS21 (SmithKline Beecham), pure QA-21 saponin purified from an extract of Quillja saponaria; DQS21 described in PCT application WO 96/33739 (SmithKline Beecham); QS-7, QS-17, QS-18 and QS-L1 (So and 10 colleagues, “Molecules and cells”, 1997, Vol. 7, p. 178-186); Freund's incomplete adjuvant; Freund's complete adjuvant; vitamin E; Montanide; alum; CpG oligonucleotides (see, for example, Kreig and 7 colleagues, Nature, Vol. 374, p. 546-549); poly-LC and derivatives thereof (e.g., poly ICLC); and various water-in-oil emulsions prepared from biodegradable oils such as squalene and/or tocopherol. Among these, Freund's incomplete adjuvant; Montanide; poly-LC and derivatives thereof; and CpG oligonucleotides are preferred. The mixing ratio between the above-described adjuvant and the polypeptide is typically about 1:10 to 10:1, preferably about 1:5 to 5:1, more preferably about 1:1. However, the adjuvant is not limited to the above-described examples, and adjuvants known in the art other than those described above may also be used when the immunity-inducing agent of the present invention is administered (see, for example, Goding, “Monoclonal Antibodies: Principles and Practice, 2nd edition”, 1986). Preparation methods for mixtures or emulsions of a polypeptide and an adjuvant are well known to those skilled in the art of vaccination.

Further, in addition to the above-described adjuvants, factors that stimulate the immune response of the subject may be used as the above-described immunoenhancer. For example, various cytokines having a property to stimulate lymphocytes and/or antigen-presenting cells may be used as the immunoenhancer in combination with the immunity-inducing agent of the present invention. A number of such cytokines capable of enhancing the immune response are known to those skilled in the art, and examples of the cytokines include, but are not limited to, interleukin-12 (IL-12), GM-CSF; IL-18, interferon-α, interferon-β, interferon-ω, interferon-γ, and Flt3 ligand, which have been shown to enhance the prophylactic action of vaccines. Such factors may also be used as the above-described immunoenhancer, and may be contained in the immunity-inducing agent of the present invention, or may be prepared as a separate composition to be administered to a patient in combination with the immunity-inducing agent of the present invention.

By bringing the above-described polypeptide into contact with antigen-presenting cells in vitro, the antigen-presenting cells can be made to present the polypeptide. That is, the polypeptides (a) to (c) described above can be used as agents for treating antigen-presenting cells. Examples of the antigen-presenting cells which may be preferably used include dendritic cells and B cells having MHC class I molecules. Various MHC class I molecules have been identified and are well-known. MHC molecules in human are called HLA. Examples of HLA class I molecules include HLA-A, HLA-B and HLA-C, more specifically, HLA-A1, HLA-A0201, HLA-A0204, HLA-A0205, HLA-A0206, HLA-A0207, HLA-A11, HLA-A24, HLA-A31, HLA-A6801, HLA-B7, HLA-B8, HLA-B2705, HLA-B37, HLA-Cw0401 and HLA-Cw0602.

The dendritic cells or B cells having MHC class I molecules can be prepared from peripheral blood by a well-known method. For example, tumor-specific dendritic cells can be induced by inducing dendritic cells from bone marrow, umbilical cord blood or patient's peripheral blood using granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-3 (or IL-4), and then adding a tumor-related peptide to the culture system.

By administering an effective amount of such dendritic cells, a response desired for therapy of a cancer can be induced. As the cells, bone marrow or umbilical cord blood donated by a healthy individual, or bone marrow, peripheral blood or the like of the patient may be used. When autologous cells of the patient are used, high safety can be attained and serious side effects are expected to be avoided. The peripheral blood or bone marrow may be any of a fresh sample, cold-stored sample and cryopreserved sample. As for the peripheral blood, whole blood may be cultured or the leukocyte components alone may be separated and cultured, and the latter is more efficient and thus preferred. Further, among the leukocyte components, mononuclear cells may be separated. In cases where the cells are originated from bone marrow or umbilical cord blood, the whole cells constituting the bone marrow may be cultured, or mononuclear cells may be separated therefrom and cultured. Peripheral blood, the leukocyte components thereof and bone marrow cells contain mononuclear cells, hematopoietic stem cells and immature dendritic cells, from which dendritic cells are originated, and also CD4-positive cells and the like. The production method for the cytokine is not restricted, and a naturally-occurring or recombinant cytokine or the like may be employed as long as its safety and physiological activity have been confirmed. Preferably, a preparation with assured quality for medical use is used in the minimum necessary amount. The concentration of the cytokine(s) to be added is not restricted as long as the dendritic cells are induced at the concentration, and usually, the total concentration of the cytokine(s) is preferably about 10 to 1000 ng/mL, more preferably about 20 to 500 ng/mL. The culture may be carried out using a well-known medium usually used for culture of leukocytes. The culturing temperature is not restricted as long as proliferation of leukocytes is possible at the temperature, and a temperature of about 37° C., which is the body temperature of human, is most preferred. The atmospheric environment during the culture is not restricted as long as proliferation of the leukocytes is possible under the environment, and the culture is preferably performed under a flow of 5% CO₂. The culturing period is not restricted as long as a necessary number of the cells are induced, and usually 3 days to 2 weeks. As for the apparatuses used for separation and culturing of the cells, appropriate apparatuses, preferably those whose safety upon application to medical uses have been confirmed and whose operations are stable and simple, may be employed. In particular, examples of the cell-culturing apparatus include not only general vessels such as Petri dishes, flasks and bottles, but also layer-type vessels, multistage vessels, roller bottles, spinner-type bottles, bag-type culturing vessels and hollow fiber columns.

The method per se to be used for bringing the above-described polypeptide into contact with the antigen presenting cells in vitro may be those well known in the art. For example, the antigen-presenting cells may be cultured in a culture medium containing the above-described polypeptide. The concentration of the peptide in the medium is not restricted, and usually about 1 to 100 μg/ml, preferably about 5 to 20 μg/ml. The cell density during the culture is not restricted and usually about 10³ to 10⁷ cells/ml, preferably about 5×10³ to 5×10⁶ cells/ml. The culture is preferably carried out according to a conventional method at 37° C. under the atmosphere of 5% CO₂. The maximum length of the peptide which can be presented on the surface of the antigen-presenting cells is usually about 30 amino acid residues. Therefore, in cases where the antigen-presenting cells are brought into contact with the polypeptide in vitro, the polypeptide may be prepared such that its length is not more than about 30 amino acid residues, although the length is not restricted.

By culturing the antigen-presenting cells in the coexistence of the above-described polypeptide, the polypeptide is incorporated into MHC molecules of the antigen-presenting cells and presented on the surface of the antigen-presenting cells. Therefore, using the above-described polypeptide, isolated antigen-presenting cells containing the complex between the polypeptide and the MHC molecule can be prepared. Such antigen-presenting cells can present the polypeptide against T cells in vivo or in vitro, to induce, and allow proliferation of, cytotoxic T cells specific to the polypeptide.

By bringing the thus prepared antigen-presenting cells having the complex between the above-described polypeptide and the MHC molecule into contact with T cells in vitro, cytotoxic T cells specific to the polypeptide can be induced and allowed to proliferate. This may be carried out by coculturing the above-described antigen-presenting cells and T cells in a liquid medium. For example, the antigen-presenting cells may be suspended in a liquid medium and placed in a vessel such as a well of a microplate, followed by adding T cells to the well and then performing culture. The mixing ratio of the antigen-presenting cells to the T cells in the coculture is not restricted, and usually about 1:1 to 1:100, preferably about 1:5 to 1:20 in terms of the cell number. The density of the antigen-presenting cells to be suspended in the liquid medium is not restricted, and usually about 100 to 10,000,000 cells/ml, preferably about 10,000 to 1,000,000 cells/ml. The coculture is preferably carried out by a conventional method at 37° C. under the atmosphere of 5% CO₂. The culturing period is not restricted, and usually 2 days to 3 weeks, preferably about 4 days to 2 weeks. The coculture is preferably carried out in the presence of one or more interleukins such as IL-2, IL-6, IL-7 and/or IL-12. In such cases, the concentration of IL-2 or IL-7 is usually about 5 to 20 U/ml, the concentration of IL-6 is usually about 500 to 2000 U/ml, and the concentration of IL-12 is usually about 5 to 20 ng/ml, but the concentrations of the interleukins are not restricted thereto. The above coculture may be repeated once to several times with addition of fresh antigen-presenting cells. For example, the operation of discarding the culture supernatant after the coculture and adding a fresh suspension of antigen-presenting cells to further conduct the coculture may be repeated once to several times. The conditions for each coculture may be the same as those described above.

By the above-described coculture, cytotoxic T cells specific to the polypeptide are induced and allowed to proliferate. Thus, using the above-described polypeptide, isolated T cells can be prepared which selectively bind to the complex between the polypeptide and the MHC molecule.

As described in the Examples below, the SCD1 gene is expressed specifically in breast cancer cells, breast cancer tissues, brain tumor cells, brain tumor tissues, colon cancer cells, colon cancer tissues, perianal adenocarcinoma tissues, perianal adenocarcinoma cells, mastocytoma tissues, mastocytoma cells, neuroblastoma cells, renal cancer cells, renal cancer tissues, liver cancer cells, liver cancer tissues, lung cancer cells, lung cancer tissues, prostate cancer cells, prostate cancer tissues and leukemia cells. Therefore, it is thought that, in these cancer species, a significantly larger amount of SCD1 exists than in normal cells. When the thus prepared cytotoxic T cells are administered to a living body such that a part of the SCD1 polypeptide present in cancer cells is presented by MHC molecules on the surface of the cancer cells, the cytotoxic T cells can damage the cancer cells using the presented polypeptide as a marker. Since the antigen-presenting cells presenting a part of the above-described SCD1 polypeptide can induce, and allow proliferation of, cytotoxic T cells specific to the polypeptide also in vivo, cancer cells can be damaged also by administering the antigen-presenting cells to a living body. That is, the cytotoxic T cells and the antigen-presenting cells prepared using the polypeptide are also effective as therapeutic and/or prophylactic agents for cancer, similarly to the immunity-inducing agent of the present invention.

In cases where the above-described isolated antigen-presenting cells or isolated T cells are administered to a living body, these are preferably prepared by treating antigen presenting cells or T cells collected from the patient to be treated, using the polypeptide (a), (b) or (c) as described above in order to avoid the immune response in the living body that attacks these cells as foreign bodies.

The therapeutic and/or prophylactic agent for cancer comprising as an effective ingredient the antigen-presenting cells or T cells is preferably administered via a parenteral administration route, for example, by intravenous or intraarterial administration. The dose is appropriately selected depending on the symptoms, the purpose of administration and the like, and is usually 1 cell to 10,000,000,000,000 cells, preferably 1,000,000 cells to 1,000,000,000 cells, which dose is preferably administered once every several days to once every several months. The formulation may be, for example, the cells suspended in physiological buffered saline, and the formulation may be used in combination with another/other anticancer preparation(s) and/or cytokine(s). Further, one or more additives well known in the field of formulation of pharmaceuticals may also be added.

Also by expressing a polynucleotide encoding any of the polypeptides (a) to (c) in the body of the subject animal, antibody production and cytotoxic T cells can be induced in the living body, and an effect comparable to that obtained in the case of administration of the polypeptide can be obtained. That is, the immunity-inducing agent of the present invention may be one comprising as an effective ingredient a recombinant vector having a polynucleotide encoding any of the polynucleotides (a) to (c), which recombinant vector is capable of expressing the polypeptide in a living body. Such a recombinant vector capable of expressing an antigenic polypeptide as shown in the later-mentioned Examples is also called a gene vaccine.

The vector used for production of the gene vaccine is not restricted as long as it is a vector capable of expressing the polypeptide in a cell of the subject animal (preferably in a mammalian cell), and may be either a plasmid vector or a virus vector, and any known vector in the field of gene vaccines may be used. The polynucleotide such as DNA or RNA encoding the above-described polypeptide can be easily prepared as mentioned above by a conventional method. Incorporation of the polynucleotide into the vector can be carried out using a method well known to those skilled in the art.

The administration route of the gene vaccine is preferably a parenteral route such as intramuscular, subcutaneous, intravenous or intraarterial administration. The dose may be appropriately selected depending on the type of the antigen and the like, and is usually about 0.1 μg to 100 mg, preferably about 1 μg to 10 mg in terms of the weight of the gene vaccine per kg body weight.

Examples of the method using a virus vector include those wherein a polynucleotide encoding the above-described polypeptide is incorporated into an RNA virus or DNA virus, such as a retrovirus, adenovirus, adeno-associated virus, herpes virus, vaccinia virus, pox virus, poliovirus or Sindbis virus, and then a subject animal is infected with the resulting virus. Among these methods, those using a retrovirus, adenovirus, adeno-associated virus, vaccinia virus or the like are especially preferred.

Examples of other methods include a method wherein an expression plasmid is directly intramuscularly administered (DNA vaccine method), and the liposome method, lipofectin method, microinjection method, calcium phosphate method and electroporation method. The DNA vaccine method and liposome method are especially preferred.

Methods for making the gene encoding the above-described polypeptide used in the present invention actually act as a pharmaceutical include in vivo methods wherein the gene is directly introduced into the body, and ex vivo methods wherein a certain kind of cells are collected from the subject animal and the gene is then introduced into the cells ex vivo, followed by returning the cells to the body (Nikkei Science, 1994, April, p. 20-45; The Pharmaceutical Monthly, 1994, Vol. 36, No. 1, p. 23-48; Experimental Medicine, Extra Edition, 1994, Vol. 12, No. 15; and references cited in these literatures, and the like). The in vivo methods are more preferred.

In cases where the gene is administered by an in vivo method, the gene may be administered through an appropriate administration route depending on the disease to be treated, symptoms and the like. The gene may be administered by, for example, intravenous, intraarterial, subcutaneous or intramuscular administration. In cases where the gene is administered by an in vivo method, the gene may be formulated into a preparation such as a solution, and in general, it is formulated into an injection solution or the like containing DNA encoding the above-described peptide of the present invention as an effective ingredient. A commonly used carrier may be also added thereto as required. In cases of a liposome or membrane fusion liposome (Sendai virus (HVJ)-liposome or the like) containing the DNA, the liposome may be formulated into a liposome preparation such as a suspension, frozen preparation or centrifugally concentrated frozen preparation.

In the present invention, “the base sequence of SEQ ID NO:1” includes not only the actual base sequence of SEQ ID NO:1, but also the sequence complementary thereto. Thus, “the polynucleotide having the base sequence of SEQ ID NO:1” includes the single-stranded polynucleotide having the actual base sequence of SEQ ID NO:1, the single-stranded polynucleotide having the base sequence complementary thereto, and the double-stranded polynucleotide composed of these single-stranded polynucleotides. When a polynucleotide encoding the polypeptide used in the present invention is prepared, any one of these base sequences is appropriately selected, and those skilled in the art can easily carry out the selection.

EXAMPLES

The present invention will now be described more concretely by way of Examples.

Example 1 Obtaining Novel Cancer Antigen Protein by SEREX Method

(1) Preparation of cDNA Library

Total RNA was extracted from testis of a dog by the acid-guanidium-phenol-chloroform method, and poly(A) RNA was purified using Oligotex-dT30 mRNA purification Kit (manufactured by Takara Shuzo Co., Ltd.) in accordance with the protocol attached to the kit.

Using the obtained mRNA (5 μg), a cDNA phage library was synthesized. For the preparation of a cDNA phage library, cDNA Synthesis Kit, Zap-cDNA Synthesis Kit, and ZAP-cDNA Gigapack III Gold Cloning Kit (manufactured by STRATAGENE) were used in accordance with the protocols attached to the kits. The size of the prepared cDNA phage library was 1×10⁶ pfu/ml.

(2) Screening of cDNA Library with Serum

Using the thus prepared cDNA phage library, immunoscreening was carried out. More specifically, the host E. coli (XL1-Blue MRF′) was infected with the library such that 2340 clones appeared on an NZY agarose plate with a size of 90 mm dia.×15 mm, and cultured at 42° C. for 3 to 4 hours to allow the phage to form plaques. The plate was covered with a nitrocellulose membrane (Hybond C Extra: manufactured by GE Healthcare Bio-Science) impregnated with IPTG (isopropyl-β-D-thiogalactoside) at 37° C. for 4 hours to allow induction and expression of proteins, and the proteins were transferred onto the membrane. Subsequently, the membrane was recovered and soaked in TBS (10 mM Tris-HCl, 1501 nM NaCl; pH 7.5) supplemented in 0.5% non-fat dry milk. The membrane was then shaken at 4° C. overnight to suppress non-specific reactions. This filter was then allowed to react with 500-fold diluted dog patient serum at room temperature for 2 to 3 hours.

As the above-described dog patient serum, serum collected from a dog patient with a perianal tumor was used. The serum was stored at −80° C. and pretreated immediately before use. The method of the pretreatment of serum was as follows. That is, the host E. coli (XL1-Blue MRF′) was infected with A, ZAP Express phage having no foreign gene inserted, and then cultured on NZY plate medium at 37° C. overnight. Subsequently, 0.2 M NaHCO₃ buffer (pH 8.3) supplemented with 0.5 M NaCl was added to the plate, and the plate was left to stand at 4° C. for 15 hours, followed by collecting the supernatant as an E. coli/phage extract. Thereafter, the collected E. coli/phage extract was passed through an NHS-column (manufactured by GE Healthcare Bio-Science) to immobilize proteins derived from the E. coli/phage thereon. The serum from the dog patient was passed through, and reacted with, this protein-immobilized column to remove antibodies that adsorb to E. coli and/or the phage. The serum fraction that passed through the column was 500-fold diluted with TBS supplemented with 0.5% non-fat dry milk, and the resulting diluent was used as the material for the immunoscreening.

The membrane on which the thus treated serum and the above-described fusion protein were blotted was washed 4 times with TBS-T (0.05% Tween 20/TBS), and reacted with goat anti-dog IgG (Goat anti Dog IgG-h+I HRP conjugated: manufactured by BETHYL Laboratories) 5,000-fold diluted with TBS supplemented with 0.5% non-fat dry milk as a secondary antibody at room temperature for 1 hour, followed by detection by enzyme coloring reaction using an NBT/BCIP reaction solution (manufactured by Roche). Colonies at positions corresponding to coloring-reaction-positive sites were recovered from the NZY agarose plate having a size of 90 mm dia.×15 mm, and dissolved in 500 μl of SM buffer (100 mM NaCl, 10 mM MgClSO₄, 50 mM Tris-HCl, 0.01% gelatin; pH 7.5). The screening was repeated as the second and third screening in the same manner as described above until a single coloring-reaction-positive colony was obtained. The isolation of the single positive clone was achieved after screening of 9110 phage clones reactive with IgG in the serum.

(3) Sequence Homology Search of Isolated Antigen Gene

To subject the single positive clone isolated by the above-described method to base sequence analysis, an operation of conversion of the phage vector to a plasmid vector was carried out. More specifically, 200 μl of a solution prepared such that the host E. coli (XL1-Blue MRF′) was contained at an absorbance OD₆₀₀ of 1.0 was mixed with 100 μl of a purified phage solution and further with 1 μl of ExAssist helper phage (manufactured by STRATAGENE), and the reaction was then allowed to proceed at 37° C. for 15 minutes. This was followed by addition of 3 ml of LB medium to the reaction mixture, and culture was performed with the resulting mixture at 37° C. for 2.5 to 3 hours. The resulting culture was immediately incubated in a water bath at 70° C. for 20 minutes. The culture was then centrifuged at 4° C. at 1,000×g for 15 minutes, and the supernatant was recovered as a phagemid solution. Subsequently, 200 μl of a solution prepared such that the phagemid host E. coli (SOLR) was contained at an absorbance OD₆₀₀ of 1.0 was mixed with 10 μl of a purified phage solution, and the reaction was allowed to proceed at 37° C. for 15 minutes. Thereafter, 50 μl of the reaction mixture was plated on LB agar medium supplemented with ampicillin (final concentration: 50 μg/ml), and culture was performed at 37° C. overnight. A single colony of transformed SOLR was recovered and cultured in LB medium supplemented with ampicillin (final concentration: 50 μg/ml) at 37° C., followed by purification of plasmid DNA having the insert of interest using QIAGEN plasmid Miniprep Kit (manufactured by Qiagen).

The purified plasmid was subjected to analysis of the full-length sequence of the insert by the primer walking method using the T3 primer of SEQ ID NO:7 and the T7 primer of SEQ ID NO:8. By this sequence analysis, the gene sequence of SEQ ID NO:1 was obtained. Using the base sequence and the amino acid sequence of this gene, homology search against known genes was carried out using a sequence homology search program BLAST (http://www.ncbi.nlm.nih.gov/BLAST/). As a result, it was revealed that the obtained gene is the SCD1 gene. Human SCD1, which is a human homologous factor of dog SCD1, had a sequence identity of 89% in terms of the base sequence and 90% in terms of the amino acid sequence; mouse SCD1, which is a mouse homologous factor, had a sequence identity of 84% in terms of the base sequence and 84% in terms of the amino acid sequence. The base sequence and the amino acid sequence of human SCD1 are shown in SEQ ID NO:3 and SEQ ID NO:4, respectively, and the base sequence and the amino acid sequence of mouse SCD1 are shown in SEQ ID NO:5 and SEQ ID NO:6, respectively.

(4) Analysis of Expression in Various Tissues

Expression of the genes obtained by the above method in dog, human and mouse normal tissues and various cell lines were investigated by the RT-PCR (Reverse Transcription-PCR) method. The reverse transcription reaction was carried out as follows. That is, from 50 to 100 mg of each tissue or 5×10⁶ to 10×10⁶ cells of each cell line, total RNA was extracted using the TRIZOL reagent (manufactured by Invitrogen) according to the protocol described in the attached instructions. Using this total RNA, cDNA was synthesized with the Superscript First-Strand Synthesis System for RT-PCR (manufactured by Invitrogen) according to the protocol described in the attached instructions. As the cDNAs of human normal tissues (brain, hippocampus, testis, colon and placenta), Gene Pool cDNA (manufactured by Invitrogen), QUICK-Clone cDNA (manufactured by CLONETECH) and Large-Insert cDNA Library (manufactured by CLONETECH) were used. The PCR reaction was carried out using primers specific to the obtained gene (the dog primers shown in SEQ ID NOs:9 and 10, the human primers shown in SEQ ID NOs:11 and 12, and the mouse primers shown in SEQ ID NOs:13 and 14) as described below. That is, the reagents and the attached buffer were mixed such that 0.25 μl of the sample prepared by the reverse transcription reaction, 2 μM each of the above primers, 0.2 mM each of dNTPs, and 0.65 U ExTaq polymerase (manufactured by Takara Shuzo Co., Ltd.) were contained in the resulting mixture in a final volume of 25 μl, and the reaction was carried out by 30 cycles of 94° C. for 30 seconds, 55° C. for 30 seconds and 72° C. for 1 minute using a Thermal Cycler (manufactured by BIO RAD). As a control for comparison, primers specific to GAPDH (the dog and human GAPDH primers are shown in SEQ ID NOs:15 and 16; and the mouse GAPDH primers are shown in SEQ ID NOs:17 and 18) were used at the same time. As a result, as shown in FIG. 1, the dog SCD1 gene was not expressed in most of the healthy dog tissues, while the gene was strongly expressed in the dog tumor tissues. Also in terms of the human and mouse SCD1 genes, the expression was not observed in most of the normal human and mouse tissues, while the expression was detected in most of the cancer cell lines (FIGS. 2 and 3), as in the case of the dog SCD1 gene.

(5) Quantitative Analysis of Expression in Various Tissues

The gene obtained by the above method was subjected to investigation of expression in human normal tissues by the quantitative RT-PCR (Reverse Transcription-PCR) method. As cDNAs for human normal tissues and cancer tissues, Tissue scan Real Time cancer survey Panel I (manufactured by ORIGENE) was used. The quantitative RT-PCR was carried out using CFX96 Real Time Cystem—C1000 Thermal Cycler, manufactured by Bio-Rad Laboratories, Inc. The PCR reaction was carried out as follows using primers specific to the obtained gene (shown in SEQ ID NOs:11 and 12). That is, 5 μl of the cDNA sample, 2 μM each of the primers, and the reagents and the buffer contained in 2×SYBR Premix Ex Tagil polymerase (manufactured by Takara Shuzo Co., Ltd.) were mixed together to prepare a mixture in a final volume of 20 μl, and the reaction was carried out by 30 cycles of 94° C. for 30 seconds, 55° C. for 30 seconds and 72° C. for 1 minute. As a result, the expression level of the SCD1 gene in each of breast cancer, colon cancer, renal cancer, liver cancer, prostate cancer and lung cancer was not less than 4 times higher than the expression level in its corresponding normal tissue. Based on these results, it can be expected that there is no concern of occurrence of side effects by antitumor agents targeting human SCD1 in normal tissues at all, and that the benefit of the pharmacological effect of the agents largely exceeds the risk of their side effects.

Example 2 Analysis of Cancer Antigenicity of SCD1 In Vivo

(1) Preparation of Recombinant Vector that Expresses SCD1 In Vivo

Based on the base sequence of SEQ ID NO:5, a recombinant vector that expresses SCD1 in vivo was prepared. PCR was prepared from the mouse cancer cell line N2a (purchased from ATCC), which showed the expression in Example 1. The reagents and the attached buffer were mixed such that 1 μl of the cDNA, 0.4 μM each of two kinds of primers having the HindIII and XbaI restriction sites (shown in SEQ ID NOs:19 and 20), 0.2 mM dNTP and 1.25 U PrimeSTAR HS polymerase (manufactured by Takara Shuzo Co., Ltd.) were contained in the resulting mixture in a final volume of 50 μl, and PCR was carried out by 30 cycles of 98° C. for 10 seconds, 55° C. for 15 seconds and 72° C. for 4 minute using a Thermal. Cycler (manufactured by BIO RAD). The above-described two kinds of primers were those for amplification of the region encoding the full-length of the amino acid sequence of SEQ ID NO:5. After the PCR, the amplified DNA was subjected to electrophoresis using 1% agarose gel, and a DNA fragment of about 1000 bp was purified using QIAquick Gel Extraction Kit (manufactured by QIAGEN).

The purified DNA fragment was ligated into a cloning vector pCR-Blunt (manufactured by Invitrogen). E. coli was transformed with the resulting ligation product, and the plasmid was then recovered. The sequence of the amplified gene fragment was confirmed to be the same as the sequence of interest by sequencing. The plasmid having the sequence of interest was treated with restriction enzymes HindIII and XbaI, and purified using QIAquick Gel Extraction Kit, followed by inserting the gene sequence of interest into a mammalian expression vector pcDNA3.1 (manufactured by Invitrogen) that had been treated with the restriction enzymes HindIII and XbaI. Use of this vector enables production of SCD1 protein in mammalian cells.

To 100 μg of the thus prepared plasmid DNA, 50 μg of gold particles (manufactured by Bio Rad), 100 μl of spermidine (manufactured by SIGMA) and 100 μl of 1 M CaCl₂ (manufactured by SIGMA) were added, and the resulting mixture was stirred by vortexing, followed by leaving the mixture to stand for 10 minutes at room temperature (the resulting particles are hereinafter referred to as the gold-DNA particles). The mixture was then centrifuged at 3000 rpm for 1 minute and the supernatant was discarded, followed by rinsing the precipitate 3 times with 100% ethanol (manufactured by WAKO). To the gold-DNA particles, 6 ml of 100% ethanol was added, and the resulting mixture was sufficiently stirred by vortexing, followed by pouring the gold-DNA particles into Tefzel Tubing (manufactured by Bio Rad) and allowing the particles to precipitate on the wall surface. Ethanol was removed by air-drying from the Tefzel Tubing to which the gold-DNA particles were attached, and the tube was then cut into pieces having a length that is appropriate for a gene gun.

(2) Antitumor Effect of SCD1 by DNA Vaccine Method

The above prepared tube was fixed in a gene gun, and the DNA vaccine was transdermally administered, by application of a pressure of 400 psi using pure helium gas, a total of 3 times at intervals of 7 days to the abdominal cavity of each of 10 individuals of A/J mice (7 weeks old, male, purchased from Japan SLC) and Balb/c mice (7 weeks old, male, purchased from Japan SLC) whose hair had been shaved (this corresponds to inoculation of 2 μg/individual of the plasmid DNA). Thereafter, a mouse neuroblastoma cell line N2a or a colon cancer cell line CT26 was transplanted to each mouse in an amount of 1×10⁶ cells to evaluate the antitumor effect (prophylactic model). For each model, plasmid DNA containing no SCD1 gene inserted was administered to 10 individuals of mice to provide a control.

The antitumor effect was evaluated based on the size of the tumor (major axis×minor axis²/and the ratio of living mice. As a result of this study, in the prophylactic model using the neuroblastoma cell line, the size of the tumor became 2966 mm³ and 759 mm³ on Day 43 in the control group and the SCD1 plasmid-administered group, respectively. Thus, remarkable regression of the tumor was observed in the SCD1 plasmid-administered group. Further, as a result of observation of survival in the prophylacetic model using the neuroblastoma cell line, it was found that all cases died by Day 74 after the administration in the control group, while 60% of the mice survived in the SCD1 plasmid-administered group. These results indicate a significant antitumor effect in the SCD1 plasmid-administered group as compared to the control group. Similarly, in the prophylactic model using the colon cancer cell line, the size of the tumor became 2518 mm³ and 604 mm³ on Day 33 in the control group and the SCD1 plasmid-administered group, respectively. Thus, remarkable regression of the tumor was observed in the SCD1 plasmid-administered group. Further, as a result of observation of survival, it was found that all cases died by Day 54 after the administration in the control group, while 50% of the mice survived in the SCD1 plasmid-administered group. These results indicate a significant antitumor effect in the SCD1 plasmid-administered group as compared to the control group.

Example 3 Preparation of Human Recombinant SCD1 Protein and Evaluation of its Immunity-Inducing Ability (1) Preparation of Human Recombinant SCD1 Protein

Based on the base sequence of SEQ ID NO:3. a recombinant protein of human SCD1 was prepared. The regents and the attached buffer were mixed such that 1 μl of the cDNA prepared in Example 1 whose expression could be confirmed for cDNAs from various tissues and cells by the RT-PCR method, 0.4 μM each of two kinds of primers having the EcoRI and XhoI restriction sites (shown in SEQ ID NOs:25 and 26), 0.2 mM dNTP and 1.25 U PrimeSTAR HS polymerase (manufactured by Takara Shuzo Co., Ltd.) were contained in the resulting mixture in a final volume of 50 and PCR was carried out by 30 cycles of 98° C. for 10 seconds, 55° C. for 15 seconds and 72° C. for 4 minute using a Thermal Cycler (manufactured by BIO RAD). The above-described two kinds of primers were those for amplification of the region encoding the full-length of the amino acid sequence of SEQ ID NO:4. After the PCR, the amplified DNA was subjected to electrophoresis using 1% agarose gel, and a DNA fragment of about 1000 bp was purified using QIAquick Gel Extraction Kit (manufactured by QIAGEN).

The purified DNA fragment was ligated into a cloning vector pCR-Blunt (manufactured by Invitrogen). E. coli was transformed with the resulting ligation product, and the plasmid was then recovered. The sequence of the amplified gene fragment was confirmed to be the same as the sequence of interest by sequencing. The plasmid having the sequence of interest was treated with restriction enzymes EcoRI and XhoI, and purified using QIAquick Gel Extraction Kit, followed by inserting the gene sequence of interest into an expression vector for E. coli, pET30a (manufactured by Novagen) that had been treated with the restriction enzymes EcoRI and XhoI. Use of this vector enables production of a His tag-fused recombinant protein. E. coli for expression, BL21 (DE3), was transformed with this plasmid, and expression was induced with 1 mM IPTG, to allow expression of the protein of interest in E. coli.

(2) Purification of Recombinant SCD1 Protein

The thus obtained recombinant E. coli that expresses SEQ ID NO:4 was cultured in LB medium supplemented with 100 μg/ml ampicillin at 37° C. until the absorbance at 600 nm reached about 0.7, and isopropyl-β-D-1-thiogalactopyranoside was then added to the culture at a final concentration of 1 mM, followed by further culturing the recombinant E. coli at 37° C. for 4 hours. Subsequently, the bacterial cells were collected by centrifugation at 4,800 rpm for 10 minutes. The pellet of the bacterial cells was suspended in phosphate-buffered saline and further subjected to centrifugation at 4,800 rpm for, 10 minutes, to wash the bacterial cells.

The bacterial cells were suspended in 50 mM Tris-HCl buffer (pH 8.0) and subjected to sonication on ice. The liquid obtained by the sonication of E. coli was centrifuged at 6000 rpm for 20 minutes, to obtain the supernatant as the soluble fraction and the precipitate as the insoluble fraction.

The insoluble fraction was suspended in 50 mM Tris-HCl buffer (pH 8.0) and then centrifuged at 6000 rpm for 15 minutes. This operation was repeated twice for removal of proteases.

The residue was suspended in 50 mM Tris-HCl buffer (pH 8.0) supplemented with 6 M guanidine hydrochloride and 0.15 M sodium chloride, and left to stand at 4° C. for 20 hours to denature protein. Thereafter, the suspension was centrifuged at 6000 rpm for 30 minutes, and the obtained soluble fraction was placed in a nickel chelate column prepared by a conventional method (carrier: Chelating Sepharose (trademark) Fast Flow (GE Health Care); column volume: 5 mL; equilibration buffer: 50 mM Tris-HCl buffer (pH 8.0) supplemented with 6M guanidine hydrochloride and 0.15 M sodium chloride), followed by leaving the resultant to stand at 4° C. overnight to allow adsorption to the nickel-chelated carrier. The column carrier was centrifuged at 1500 rpm for 5 minutes and the resulting supernatant was recovered. The column carrier was then suspended in phosphate-buffered saline and refilled into the column.

The fraction not adsorbed to the column was washed with 10 column volumes of 0.1 M acetate buffer (pH 4.0) supplemented with 0.5 M sodium chloride, and immediately thereafter, elution with 0.1 M acetate buffer (pH 3.0) supplemented with 0.5 M sodium chloride was carried out to obtain a purified fraction, which was used later as the material for an administration test. The presence of the protein of interest in each eluted fraction was confirmed by Coomassie staining carried out according to a conventional method.

The buffer of the purified preparation obtained by the above method was replaced with a reaction buffer (50 mM Tris-HCl, 100 mM NaCl, 5 mM CaCl₂ (pH8.0)), and the resulting sample was subjected to cleavage of the His tag with factor Xa protease and purification of the protein of interest, using Factor Xa Cleavage Capture Kit (manufactured by Novagen) in accordance with the protocol attached to the kit. Subsequently, the buffer of 12 ml of the purified preparation obtained by the above method was replaced with physiological phosphate buffer (manufactured by Nissui Pharmaceutical) using ultrafiltration NANOSEP 10K OMEGA (manufactured by PALL), and the resulting sample was subjected to aseptic filtration through HT Tuffryn Acrodisc 0.22 μm (manufactured by PALL) and used in the experiment.

(3) Induction of CD8-Positive Cytotoxic T Cells Reactive with Human Recombinant SCD1 Protein

From a healthy individual, peripheral blood was separated, and the peripheral blood was overlaid on Lymphocyte separation medium (OrganonpTeknika, Durham, N.C.), followed by centrifuging the resultant at 1,500 rpm at room temperature for 20 minutes. A fraction containing peripheral blood mononuclear cells (PBMCs) was recovered and washed 3 (or more) times in cold phosphate buffer, to obtain PBMCs. The obtained PBMCs were suspended in 20 ml of AIM-V medium (Life Technologies, Inc., Grand Island, N.Y., USA), and the cells were allowed to adhere to a culture flask (Falcon) at 37° C. in 5% CO₂ for 2 hours. Nonadherent cells were used for preparation of T cells, and adherent cells were used for preparation of dendritic cells.

On the other hand, the adherent cells were cultured in AIM-V medium in the presence of IL-4 (1000 U/ml) and GM-CSF (1000 U/ml). Nonadherent cells obtained 6 days later were collected, and the human recombinant SCD1 protein was added to the cells at a concentration of 10 μg/ml, followed by culturing the cells at 37° C. in 5% CO₂ for 4 hours. Thereafter, the medium was replaced with AIM-V medium supplemented with IL-4 (1000 U/ml), GM-CSF (1000 U/ml), IL-6 (1000 U/ml, Genzyme, Cambridge, Mass.), IL-113 (10 ng/ml, Genzyme, Cambridge, Mass.) and TNF-α (10 ng/ml, Genzyme, Cambridge, Mass.), and the culture was carried out for additional 2 days to obtain a population of nonadherent cell to be used as dendritic cells.

The prepared dendritic cells were suspended in AIM-V medium at a cell density of 1×10⁶ cells/ml, and the human recombinant SCD1 protein was added again at a concentration of 10 μg/ml to the suspension. Using a 96-well plate, the cells were cultured at 37° C. in 5% CO₂ for 4 hours. After the culture. X-ray irradiation (3000 rads) was carried out, and the cells were washed with AIM-V medium, followed by suspension in AIM-V medium supplemented with 10% human AB serum (Nabi, Miami, Fla.), IL-6 (1000 U/ml) and IL-12 (10 ng/ml, Genzyme, Cambridge, Mass.). The cells were then placed in a 24-well plate in an amount of 1×10⁵ cells/well. Further, the prepared T cell population was added to each well in an amount of 1×10⁶ cells, and cultured at 37° C. in 5% CO₂. Each culture supernatant was discarded 7 days later, and dendritic cells obtained in the same manner as described above by treatment with the human SCD1 protein and the subsequent X-ray irradiation were suspended in AIM-V medium supplemented with 10% human AB serum (Nabi, Miami, Fla.), IL-7 (10 U/ml, Genzyme, Cambridge, Mass.) and IL-2 (10 U/ml, Genzyme, Cambridge, Mass.) (cell density, 1×10⁵ cells/ml). The resulting suspension was added to the 24-well plate in an amount of 1×10⁵ cells/well, and the cells were further cultured. After repeating the same operation 4 to 6 times at intervals of 7 days, stimulated T cells were recovered, and induction of CD8-positive T cells was confirmed by flow cytometry.

As a negative control, a protein having a sequence that is outside the scope of the present invention was used (SEQ ID NO:27).

Subsequently, whether or not the CD8-positive T cells stimulated with the present polypeptide can damage SCD1-expressing tumor cells was studied.

In a 50-ml centrifuge tube, 10⁵ cells of a human glioma cell line, U-87MG (purchased from ATCC), in which expression of SCD1 was confirmed, were collected, and 100 μCi chromium 51 was added to the cells, followed by incubation of the resulting mixture at 37° C. for 2 hours. Thereafter, the cells were washed 3 times with AIM-V medium supplemented with 10% human AB serum, and placed in a 96-well V-bottom plate in an amount of 10³ cells per well. Subsequently, 10⁵, 5×10⁴, 2.5×10⁴ or 1.25×10⁴ CD8-positive T cells that were stimulated with the human recombinant SCD1 protein and suspended in AIM-V medium supplemented with 10% human AB serum were added to each well, and culture was performed at 37° C. in 5% CO₂ for 4 hours. Thereafter, the amount of chromium 51 released from damaged tumor cells in the culture supernatant was measured using a gamma counter to calculate the cytotoxic activity of the CD8-positive T cells stimulated with the human recombinant SCD1 protein.

As a result, it was found that the CD8-positive T cells stimulated with the human recombinant SCD1 protein had cytotoxic activity against U-87MG. On the other hand, the CD8-positive T cells induced using the negative control protein (SEQ ID NO:27) did not show cytotoxic activity. Thus, it was revealed that the human recombinant SCD1 protein used in the present invention has a capacity to induce CD8-positive cytotoxic T cells that can damage tumor cells.

The cytotoxic activity means the cytotoxic activity of the CD8-positive T cells against T98G determined by: mixing 10⁵ CD8-positive T cells stimulated and induced as described above, with 10³ cells of the malignant brain tumor cell line U-87MG into which chromium 51 was incorporated; culturing the resulting mixture for 4 hours; measuring the amount of chromium 51 released to the medium after the culture; and then performing calculation according to Equation 1.

Cytotoxic activity (%)=amount of chromium 51 released from U-87MG after addition of CD8-positive T cells (cpm)/amount of chromium 51 released from target cells after addition of 1 N hydrochloric acid (cpm)×100.  Equation 1

INDUSTRIAL APPLICABILITY

The present invention is useful for therapy and/or prophylaxis of cancer since the present invention provides an immunity-inducing agent containing a polypeptide that exerts antitumor activity against various cancers. 

1. An immunity-inducing agent comprising as an effective ingredient(s) at least one polypeptide having immunity-inducing activity selected from the polypeptides (a) to (c) below, and/or a recombinant vector(s) that comprise(s) a polynucleotide(s) encoding said at least one polypeptide, said recombinant vector(s) being capable of expressing said polypeptide(s) in vivo: (a) a polypeptide composed of not less than 7 consecutive amino acids in any one of the amino acid sequences of SEQ ID NOs:4, 2, 22 and 24 in SEQUENCE LISTING; (b) a polypeptide having a sequence identity of not less than 85% to said polypeptide (a) and composed of not less than 7 amino acids; and (c) a polypeptide comprising said polypeptide (a) or (b) as a partial sequence thereof.
 2. The immunity-inducing agent according to claim 1, wherein said polypeptide having immunity-inducing activity is a polypeptide having the amino acid sequence of SEQ ID NO:4, 2, 22 or 24 in SEQUENCE LISTING.
 3. The immunity-inducing agent according to claim 1, which is an agent for treating antigen-presenting cells.
 4. The immunity-inducing agent according to claim 1, which is a therapeutic and/or prophylactic agent for a cancer(s).
 5. The immunity-inducing agent according to claim 4, wherein said cancer(s) is/are a cancer(s) expressing SCD1.
 6. The immunity-inducing agent according to claim 4, wherein said cancer(s) is/are breast cancer, brain tumor, colon cancer, perianal adenocarcinoma, neuroblastoma, mastocytoma, renal cancer, liver cancer, lung cancer, prostate cancer and/or leukemia.
 7. The immunity-inducing agent according to claim 1, further comprising an immunoenhancer.
 8. The immunity-inducing agent according to claim 7, wherein said immunoenhancer is at least one selected from the group consisting of Freund's incomplete adjuvant; Montanide; poly-I:C and derivatives thereof; CpG oligonucleotides; interleukin-12; interleukin-18; interferon-α; interferon-β; interferon-ω; interferon-γ; and Flt3 ligand.
 9. The immunity-inducing agent according to claim 2, which is an agent for treating antigen-presenting cells.
 10. The immunity-inducing agent according to claim 2, which is a therapeutic and/or prophylactic agent for a cancer(s).
 11. The immunity-inducing agent according to claim 5, wherein said cancer(s) is/are breast cancer, brain tumor, colon cancer, perianal adenocarcinoma, neuroblastoma, mastocytoma, renal cancer, liver cancer, lung cancer, prostate cancer and/or leukemia.
 12. The immunity-inducing agent according to claim 2, further comprising an immunoenhancer.
 13. The immunity-inducing agent according to claim 3, further comprising an immunoenhancer.
 14. The immunity-inducing agent according to claim 4, further comprising an immunoenhancer.
 15. The immunity-inducing agent according to claim 5, further comprising an immunoenhancer.
 16. The immunity-inducing agent according to claim 6, further comprising an immunoenhancer. 